The chronicle of John of Fordun (14th century) mentions Giric as "Grim" or "Gryme", reporting him killed by King Malcolm II.
John Bannerman theorised that mac Duib, the Gaelic patronymic of Kenneth III, evolved to the surnames Duff and MacDuff, and that Kenneth III could be a direct ancestor to Clan MacDuff, which produced all mormaers and earls of Fife from the 11th to the mid-14th century, noting that Giric could be the actual founder of the house, following a pattern of several Scottish clans seemingly founded by grandsons of their eponym.
[9] Kenneth III was killed in battle at Monzievaird in Strathearn by king Malcolm II (Máel Coluim mac Cináeda), which took place about 25 March 1005.
Andrew of Wyntoun reported that Malcolm III (reigned 1058–1093) had granted to a "MacDuff, thane of Fife" the privilege of enthroning the kings at their inauguration.
John of Fordun has Malcolm III promise this same unnamed MacDuff that he will be the first man of the kingdom, second only to the king.
Bannerman suggests that the MacDuffs had their own, legitimate claim to the Scottish throne, which they declined to pursue, having been compensated with privileges by Malcolm III and his descendants.
John of Fordun claims that Kenneth II of Scotland (reigned 971–995) attempted to establish new succession rules, which would limit the right to the throne to his own descendants, excluding all other claimants.
[15] The contemporary kings of Strathclyde were also involved in the feud, though it is uncertain whether they had dynastic connections with the various Scottish rival lines.
A theory that they represented another line of descendants of Donald II of Scotland (reigned 889–900)[15] was based on the idea that Owen I of Strathclyde (d. 937) was the son of this king.